Technical Abstract:
There have been many excellent reviews written on the status of biological control of weeds with plant pathogens. Themes of these reviews include “success” of programs as defined ultimately by registration of a product and commercial viability. Many candidate organisms fail to reach this end, so reviewers may also discuss the many limitations and challenges encountered in the process of developing candidates as bioherbicides. In some instances, biological control agents perform well when used on a small-scale, such as in laboratory or greenhouse trials, but do not retain the same level of activity when applied in the field. There are several possible explanations for this, including the impact of the changes associated with macro- and micro-environments, the methods or substrates used for large-scale culture of the organism, and, possibly more important and often overlooked, factors associated with leaf-surface ecology, including the potential negative effects of epiphytic microflora and fauna on the applied bioherbicidal agent. Although there are biological and environmental limitations in any given bioherbicide system, many pathogens retain a high level of efficacy, yet never result in a “successful” bioherbicide, meaning one for which the end result of the research is a commercial product sold for widespread use at a profit. It is possible that this is a result of political complications, regulatory requirements, and business concerns. There is an expectation that a bioherbicide product will perform in a manner similar to chemical herbicides. An evaluation of the “success” of weed biological control work must also acknowledge the scientific contributions that the field of study has made to each of the various disciplines it embraces (e.g. plant pathology, weed science, ecology, and agriculture to name a few). Another measure of success is the formation of scientists into an international community that been the source of many major scientific contributions through research on plant pathogens for weed control, even if these works have not resulted in the expected plethora of commercially sustainable, “successful” products. Dr. Raghavan Charudattan has had a profound influence on the cohesion of this group of researchers, as a founder of the journal Biological Control: Theory and Application of Pest Management, as well as a leader in the development of this approach to weed control.